The present invention relates to a high frequency power amplifying apparatus for a multi-band communication system or a multi-mode communication system, and a radio communication apparatus in which the high frequency power amplifying apparatus is incorporated. Particularly the invention relates to a technique which is effective in applications to a high frequency power amplifying apparatus (high frequency power amplifying module: PA module) with a plurality of amplifying sections, such as one for a dual-band communication system, and a radio communication apparatus, such as a mobile communication apparatus, in which the high frequency power amplifying apparatus is incorporated.
A high frequency power amplifier is used in a transmitter portion of a mobile communication apparatus such as a mobile telephone, a portable telephone, or the like.
A dual-band communication system is known as a system which can establish communication between portable telephones (for example, cellular telephones) which are different in communication system. Such a dual-band system is described, for example, in xe2x80x9cTHE HITACHI HYORONxe2x80x9d by Hitachi Hyoron-sha, Vol. 80, No. 11 (1998), pp. 47-52. In the same document, there is description about a dual-band system and a dual-band high frequency power amplifier (RF module: PA module) which are based on GSM (Global System for Mobile Communications) having a carrier frequency band in a range of from 880 MHz to 915 MHz and DCS-1800 (Digital Cellular System 1800) having a carrier frequency band in a range of from 1,710 MHz to 1,785 MHz. The document also discloses a triple-mode system as a composite apparatus.
On the other hand, JP-A-11-186921 (published on Jul. 9, 1999) discloses a multi-band mobile communication apparatus which is available for portable telephone systems such as PCN (Personal Communications Network: DCS-1800), PCS (Personal Communications Service: DCS-1900), GSM, and so on.
A dual-band high frequency power amplifying module is configured to have two amplifying sections (high frequency power amplifying sections) each constituted by two or more transistors (amplifiers) connected in cascade sequentially.
In the background art, in order to apply control voltages to transistors in respective stages independently of one another, a general high frequency power amplifying apparatus (RF power amplifier module) divides the voltage of a power control signal Vapc by resistors to thereby supply desired gate biases to the transistors.
Such a configuration has an advantage that gate biases to the transistors in the respective stages can be established independently of one another. However, an electric current also flows into the gates of the respective transistors. Accordingly, when such a configuration is applied to a dual or more RF power amplifier having two amplifying sections, a power control current Iapc becomes unable to satisfy the current consumption specification.
If the resistance of a control voltage supply circuit is to be increased to solve the above-mentioned problem, the CR time constant defined by the resistance and the gate-to-drain parasitic capacitance of a MOS transistor is increased. As a result, a request to the transistor for the switching rate cannot be performed satisfactorily.
It is an object of the present invention to provide a high frequency power amplifying apparatus with a plurality of amplifying sections in which biases of transistors in the respective amplifying sections can be set to be proper enough to attain high linearity.
It is another object of the present invention to provide a high frequency power amplifying apparatus with a plurality of amplifying sections, which is superior in switching characteristic.
It is a further object of the present invention to provide a high frequency power amplifying apparatus with a plurality of amplifying sections, in which only one switching terminal is provide and which is convenient to use.
It is a still further object of the present invention to provide a high frequency power amplifying apparatus with a plurality of amplifying sections, which can achieve reduction of the power consumption.
It is another object of the present invention to provide a radio communication apparatus for a multi-band communication system or a multi-mode communication system, which is superior in performance and which can reduce the power consumption.
In a high frequency power amplifying apparatus with amplifying sections each having a plurality of amplifying stages connected in cascade, a power control signal is supplied to the amplifying sections through a control terminal so as to control the output of the high frequency power amplifying apparatus. According to an aspect of the present invention, in the light of the fact that the respective amplifying stages in the amplifying sections are usually formed in the same manufacturing process with a result that earlier preceding amplifying stages have larger gain, dividing resistors are connected in series with each other between the control terminal and a reference potential to divide the voltage of the power control signal so as to generate a plurality of different gain control signals. Each amplifying stage is supplied with one of the gain control signals thus generated. The voltage of the gain control signal supplied to an amplifying stage has a smaller absolute value than that of the gain control signal supplied to an earlier preceding stage.
According to another aspect of the present invention, there is provided a high frequency power amplifying apparatus comprising:
a plurality of amplifying stages including at least first and final stages, each of the plurality of amplifying stages having a first terminal for receiving an input signal to the stage, a second terminal for sending out an output signal of the stage, and a third terminal for receiving a reference potential for the stage, the first terminal of the first stage being adapted to receive a high frequency input signal to the high frequency power amplifying apparatus, the second terminal of the final stage being adapted to send out a high frequency output signal of the high frequency power amplifying apparatus, the second terminal of each amplifying stage except the final stage being electrically connected to the first terminal of a stage succeeding thereto, each of the amplifying stages except said first stage having a gain smaller than that of a stage preceding thereto;
a control terminal for receiving a power control signal; and
a plurality of dividing resistors connected in series with one another between the control terminal and a reference potential for dividing a voltage of the power control signal to thereby generate a plurality of different gain control signals, different ones of the plurality of gain control signals being supplied to different ones of the first terminals of the plurality of amplifying stages respectively, an absolute value of a voltage of the gain control signal applied to the first terminal of each stage being smaller than that of the gain control signal applied to the first terminal of an earlier preceding stage.
According to another aspect of the present invention, there is provided a high frequency power amplifying apparatus comprising:
a first amplifying section having a plurality of amplifying stages each including at least first and final stages, each of the plurality of amplifying stages having a first terminal for receiving an input signal to the stage and a bias signal for the stage, a second terminal for sending out an output signal of the stage and a third terminal for receiving a reference potential for the stage, the first terminal of the first stage being adapted to receive a first high frequency input signal to the high frequency power amplifying apparatus, the second terminal of the final stage being adapted to send out a first high frequency output signal of the high frequency power amplifying apparatus, the second terminal of each amplifying stage except the final stage being electrically connected to the first terminal of a stage succeeding thereto, each of the amplifying stages except the first stage having a gain smaller than that of a stage preceding thereto;
a second amplifying section having a plurality of amplifying stages each including at least first and final stages, each of the plurality of amplifying stages having a first terminal for receiving an input signal to the stage and a bias signal for the stage, a second terminal for sending out an output signal of the stage and a third terminal for receiving a reference potential for the stage, the first terminal of the first stage being adapted to receive a second high frequency input signal to the high frequency power amplifying apparatus, the second terminal of the final stage being adapted to send out a second high frequency output signal of the high frequency power amplifying apparatus, the second terminal of each amplifying stage except the final stage being electrically connected to the first terminal of a stage succeeding thereto, each of the amplifying stages except the first stage having a gain smaller than that of a stage preceding thereto;
a control terminal for receiving a power control signal;
a first series of dividing resistors connected in series with one another between the control terminal and a reference potential for dividing a voltage of the power control signal to thereby generate a plurality of different first gain control signals, different ones of the plurality of first gain control signals being supplied as the bias signals to the respective first terminals of the plurality of amplifying stages in the first amplifying section, an absolute value of a voltage of the first gain control signal applied to the first terminal of each stage being smaller than that of the first gain control signal applied to the first terminal of an earlier preceding stage;
a second series of dividing resistors connected in series with one another between the control terminal and the reference potential for dividing a voltage of the power control signal to thereby generate a plurality of different second gain control signals, different ones of the plurality of second gain control signals being supplied as the bias signal to the respective first terminals of the plurality of amplifying stages in the second amplifying section, an absolute value of a voltage of the second gain control signal applied to the first terminal of each stage being smaller than that of the second gain control signal applied to the first terminal of an earlier preceding stage;
a selection circuit connected to the first and second series of series-connected resistors, said selection circuit being responsive to an amplifying-section selection signal to cause the power control signal to be supplied to one of the first series of series-connected resistors and the second series of series-connected resistors and cause the power control signal to be blocked from being supplied to the other of the first and second series of series-connected resistors in order to make one of the first and second amplifying sections active and make the other inactive.